Do chlorides corrode stainless steel?
Wet and humid environments containing chloride ions can cause pitting corrosion and crevice corrosion of austenitic stainless steel components. Components under an applied or residual stress can deteriorate further by stress corrosion cracking in these conditions.
What causes chloride stress corrosion cracking?
Chloride stress corrosion cracking (CSCC) is a type of intergranular corrosion. Chloride stress corrosion involves selective attack of a metal along its grain boundaries. It occurs in austenitic stainless steel under tensile stress in the presence of oxygen, chloride ions and high temperature.
What stainless steel group has the best chloride stress corrosion cracking resistance?
Austenitic grades with relatively high nickel and molybdenum contents such as alloy 20, 904L, and the 6% molybdenum super austenitic grades have substantially better chloride SCC resistance. The ferritic family of stainless steels, which includes grades such as type 430 and 444 is very resistant to chloride SCC.
How does chlorine corrode stainless steel?
Chlorine affects stainless steel because it breaks down what is known as the ‘passive film’ on the surface of stainless steel. And once this happens, the stainless steel is vulnerable to corrosion and further pitting and damage.
How do chlorides affect corrosion?
Chloride ions intensify corrosion by diffusing into the crevice, attracted by the metal ions produced there.
What is needed for stress corrosion cracking?
Stress corrosion cracking (SCC) results from the combined action of three factors: Tensile stresses in the material. A corrosive medium – especially chloride-bearing or hydrogen-sulphide (H2S) media. Chloride-induced SCC normally occurs above 60°C (140ºF).
How do you prevent stress corrosion cracking in stainless steel?
Stress corrosion cracking can be prevented through:
- Avoid the chemical species that causes SCC.
- Control of hardness and stress level (residual or load).
- Introduce compressive stress by shot-peening for example.
- Use of materials known not to crack in the specified environment.
Does stainless steel react with chlorine?
Chlorine is very aggressive to stainless steels. Much higher concentrations can be used for short periods as the attack on the stainless steel must initiate and form a stable pit for failure to occur.
Will stainless steel rust in a chlorine pool?
Although stainless steel is more resistant to chlorine than other metals, pitting corrosion can occur at very high chlorination levels and pool water chemistry should be carefully monitored.
Is chloride corrosive to metal?
Gaseous chlorine at low temperatures and in the absence of moisture is not particularly corrosive and is commonly handled in carbon steel. If any water is present, however, chlorine becomes aggressive to many metals. Similarly, dry hydrogen chloride (HCl) is not corrosive to most metals.
Does chloride corrode metal?
Low levels of chloride tend to cause general corrosion while high levels of chloride likely induce localized corrosion. However, no strict boundaries exist between the general and localized process along with higher chloride concentrations and prolonged exposure time.
What is chloride stress cracking?
Chloride stress corrosion cracking (CLSCC) is one the most common reasons why austenitic stainless steel pipework and vessels deteriorate in the chemical processing and petrochemical industries. Deterioration by CLSCC can lead to failures that have the potential to release stored energy and/or hazardous substances.
Does chlorine cause stainless steel to rust?
When chloramines accumulate on stainless surfaces, superficial brown corrosion staining can appear. This mild corrosion will not impair the structural integrity of the stainless steel surfaces. One should avoid cleaning products containing hydrochloric acid or chloride compounds, which can cause corrosion or increase chloramine adherence.
What causes stainless steel corrosion?
the time to first leak or perforation;
What can corrode stainless steel?
– A pH value less than 4.5 – A resistivity less than 2000 Ω · cm – High moisture content – Presence of chlorides, sulphides and bacteria – Presence of stray currents.